Bubble nucleation on nano- to micro-size cavities and posts: An experimental validation of classical theory

Witharana, Sanjeeva; Phillips, Brent; Strobel, Sebastian; Kim, H. D.; McKrell, Thomas; Chang, Jae-Byum; Buongiorno, Jacopo; Berggren, Karl K.; Chen, L.; Ding, Yulong

doi:10.1063/1.4752758

Cited by 49 publications

(20 citation statements)

References 8 publications

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“…1). It is well known that in nucleate boiling the nucleation of bubbles occurs preferentially at microcavities present on the surface [2]; in the absence of such cavities or in case those cavities are flooded, the temperature of nucleation can be much higher than the stable equilibrium (saturation) temperature of the liquid-vapor mixture, depending on the actual size of the cavities [2,3] and the surface energy (wettability) of the surface material [2]. As the bubble grows at the wall, pinning of the triple-phase contact line can occur at the base of the bubble, if roughness features and/or heterogeneities are present on the surface [4,5].…”

Section: Introductionmentioning

confidence: 99%

Can corrosion and CRUD actually improve safety margins in LWRs?

Buongiorno

2014

Annals of Nuclear Energy

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It is well known that boiling and quenching heat transfer depends strongly on the morphology and composition of the solid surface through which the heat transfer occurs. The relevant surface features are roughness, wettability (hydrophilicity), porosity, presence of cavities, size and shape of cavities, and thermo-physical properties of the surface material. Recent work at MIT has explored the separate effects of surface roughness, wettability and porosity on both Critical Heat Flux (CHF) and quenching heat transfer (Leidenfrost point temperature). Briefly, interconnected porosity within a hydrophilic matrix greatly enhances the CHF limit (by as much as 60%) and the Leidenfrost temperature (by as much as 150C). Surprisingly, surface roughness has a comparably minor effect on both CHF and quenching. There are opportunities to exploit in Light Water Reactor (LWR) nuclear plants, where CHF and quenching determine the thermal margins during loss-of-flow and loss-of-coolant accidents, respectively, and the surface of the fuel naturally develops porous hydrophilic layers because of CRUD deposition and corrosion. This paper reviews the MIT experimental database generated using engineered surfaces with carefully-controlled characteristics, and discuss its applications to LWR safety, both design-basis and beyond-design-basis accidents.

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Section: Introductionmentioning

confidence: 99%

Can corrosion and CRUD actually improve safety margins in LWRs?

Buongiorno

2014

Annals of Nuclear Energy

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“…Therefore, it can be deduced that a larger cavity tends to have a lower nucleation temperature assuming that the radius of curvature of trapped gas is the same as the radius of cavity. As indicated by the results of S. Witharana et al 43,. the bubble nucleation temperature decreases when the diameter of the cavity increases.…”

Section: Discussionmentioning

confidence: 73%

Atomization of High-Viscosity Fluids for Aromatherapy Using Micro-heaters for Heterogeneous Bubble Nucleation

Law

Kong

Chan

et al. 2017

Sci Rep

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The development of a novel lead-free microelectromechanical-system (MEMS)-based atomizer using the principle of thermal bubble actuation is presented. It is a low-cost, lead-free design that is environmentally friendly and harmless to humans. It has been tested to be applicable over a wide range of fluid viscosities, ranging from 1 cP (e.g., water) to 200 cP (e.g., oil-like fluid) at room temperature, a range that is difficult to achieve using ordinary atomizers. The results demonstrate that the average power consumption of the atomizer is approximately 1 W with an atomization rate of 0.1 to 0.3 mg of deionized (DI) water per cycle. The relationships between the micro-heater track width and the track gap, the size of the micro-cavities and the nucleation energy were studied to obtain an optimal atomizer design. The particle image velocimetry (PIV) results indicate that the diameter of the ejected droplets ranges from 30 to 90 μm with a speed of 20 to 340 mm/s. In addition, different modes of spraying are reported for the first time. It is envisioned that the successful development of this MEMS-based atomizing technology will revolutionize the existing market for atomizers and could also benefit different industries, particularly in applications involving viscous fluids.

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“…Since then, cavity and surface fabrication methods have been refined, facilitating controlled nucleation experiments. An example of this is the recent work by Witharana et al (2012), where the classical theory for bubble nucleation was validated for nano-to micro-size cavities.…”

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confidence: 96%

Heat-flux enhancement by vapour-bubble nucleation in Rayleigh–Bénard turbulence

et al. 2015

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We report on the enhancement of turbulent convective heat transport due to vapour-bubble nucleation at the bottom plate of a cylindrical Rayleigh-Bénard sample (aspect ratio 1.00, diameter 8.8 cm) filled with liquid. Microcavities acted as nucleation sites, allowing for well-controlled bubble nucleation. Only the central part of the bottom plate with a triangular array of microcavities (etched over an area with diameter of 2.5 cm) was heated. We studied the influence of the cavity density and of the superheat T b − T on (T b is the bottom-plate temperature and T on is the value of T b below which no nucleation occurred). The effective thermal conductivity, as expressed by the Nusselt number Nu, was measured as a function of the superheat by varying T b and keeping a fixed difference T b − T t 16 K (T t is the top-plate temperature). Initially T b was much larger than T on (large superheat), and the cavities vigorously nucleated vapour bubbles, resulting in two-phase flow. Reducing T b in steps until it was below T on resulted in cavity deactivation, i.e. in one-phase flow. Once all cavities were inactive, T b was increased again, but they did not reactivate. This led to one-phase flow for positive superheat. The heat transport of both one-and two-phase flow under nominally the same thermal forcing and degree of superheat was measured. The Nusselt number of the two-phase flow was enhanced relative to the one-phase system by an amount that increased with increasing T b . Varying the cavity density (69, 32, 3.2, 1.2 and 0.3 mm −2 ) had only a small effect on the global Nu enhancement; it was found that Nu per active site decreased as the cavity density increased. The heat-flux enhancement of an isolated nucleating site was found to be limited by the rate at which the cavity could generate bubbles. Local bulk temperatures of one-and two-phase flows were measured at two positions along the vertical centreline. Bubbles increased the liquid temperature (compared to one-phase † Email address for correspondence: daniela.narezo@gmail.com 332 D. Narezo Guzman and others flow) as they rose. The increase was correlated with the heat-flux enhancement. The temperature fluctuations, as well as local thermal gradients, were reduced (relative to one-phase flow) by the vapour bubbles. Blocking the large-scale circulation around the nucleating area, as well as increasing the effective buoyancy of the two-phase flow by thermally isolating the liquid column above the heated area, increased the heat-flux enhancement.

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Bubble nucleation on nano- to micro-size cavities and posts: An experimental validation of classical theory

Cited by 49 publications

References 8 publications

Can corrosion and CRUD actually improve safety margins in LWRs?

Can corrosion and CRUD actually improve safety margins in LWRs?

Atomization of High-Viscosity Fluids for Aromatherapy Using Micro-heaters for Heterogeneous Bubble Nucleation

Heat-flux enhancement by vapour-bubble nucleation in Rayleigh–Bénard turbulence

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